1. Field of the Invention
The present invention relates to systems and methods for mitigating the effects of packet loss on an audio signal, such as a speech signal, that is transmitted between terminals in a wireless communication system. The present invention also relates to systems and methods for reducing the amount of power consumed by such terminals.
2. Background
In wireless communication systems that include battery-operated terminals, a major design consideration for the terminals is minimizing power consumption. For example, in a Bluetooth® wireless communication system, it is desirable to reduce the amount of power consumed by a battery-operated Bluetooth® terminal (such as a Bluetooth® headset) in order to enable longer periods of use between battery recharging or replacement.
In many wireless communication systems, impairments on a wireless channel can result in the loss of packets transmitted between terminals. Where the packets carry information representative of an audio signal, such as a speech signal, such packet loss can result in a perceptible reduction in the quality and intelligibility of the audio signal when played back to a user. To address this issue, some of these systems provide a mechanism by which a transmitting terminal can retransmit lost packets to a receiving terminal. For example, version 1.2 of the Bluetooth® Core Specification and all subsequent versions thereof define an audio transport mechanism—termed the Extended Synchronous Connection Oriented (eSCO) channel—that allows for the retransmission of lost packets between Bluetooth® terminals. This functionality can significantly improve the reliability of a wireless link between the two terminals, thereby facilitating the delivery of high-quality audio content, such as speech, even in poor transmission conditions. Unfortunately, however, implementation of the retransmission scheme increases power consumption by both terminals.
Terminals in wireless communication systems that transport speech or audio may also employ Packet Loss Concealment (PLC) to conceal the effects of lost packets on an audio signal. PLC algorithms take advantage of redundancy in a received audio waveform to conceal the effects of the lost data on the audio signal. While current state-of-the-art PLC algorithms perform reasonably well in mitigating the effects of packet loss on an audio stream, such algorithms are typically not capable of delivering the same level of quality as a retransmission scheme when the level of impairment on the wireless channel becomes significant.
What is needed, then, is an improved system and method for mitigating the effects of packet loss on an audio signal transmitted between terminals in a wireless communication system. In particular, the desired system and method should operate more robustly than conventional state-of-the art PLC algorithms during significant channel impairments but also consume less terminal power as compared to conventional retransmission schemes.